Dec. 6, i ? i 5 Influence of Growth of Cowpeas on Soil Properties 
445 
and should be an index to friability (Table IV). Wollny compared the 
porosity of cores similarly taken by measuring the relative amounts of 
water needed to fill the pore space, but the principle is the same in 
both cases. 
Table IV.— Apparent specific gravity of soil under various treatments as determined on 
October 15 , 1912 
Plot No. and treatment. 
Weight of soil. 
Average 
weight of 
core. 
Apparent 
specific 
gravity. 
Core No. 1. 
Core No. 2. 
D (unplowed; clean). 
B (unplowed; cowpeas). 
F (plowed; cowpeas). 
F (plowed; shade). 
G (plowed; clean). 
Gm. 
i >957 
1,865 
1,720 
1,740 
1.63S 
Gm. 
1.936 
1, 884 
h 739 
1.752 
1, 742 
Gm. 
1,946 
I, 884 
1,729 
1,746 
1.756 
I- 33 
1. 26 
I. 17 
1. 18 
1. 19 
Checking the results found by the Wollny method with those shown 
in Table III, the same ratio is found to hold in every case. This gives 
strong assurance that the use of the compactness device, by means of 
which the results of Table III were obtained, is an accurate method of 
measuring soil friability, and, in that it is easily and rapidly made, a 
very desirable one. 
Table V. —Percentage of moisture in the various experimental plots on October 15, 1912 
Plot No. and treatment. 
Percentage of moisture. 
First foot. 
Second foot. 
Third foot. 
Fourth foot. 
D (unplowed; clean). 
17.9 
29.4 
24. 2 
22. 5 
B (unplowed; cowpeas). 
25. 2 
28. I 
17.9 
13. 6 
F (plowed; cowpeas). 
21. 7 
26. I 
16. 5 
18. 8 
G (plowed; shade). 
19. 2 
29. O 
25-9 
26. 9 
H (plowed; clean). 
II. 2 
28. 3 
27.9 
25-3 
A study of the moisture in the soil at the close of the experiment, as 
shown by Table V, reveals, as would be expected, that the plots in cow- 
peas leave less moisture in the soil than do the un cropped plots kept 
clean. However, this use of water is from below the second foot. Under 
cowpeas the surface foot, as well as the second foot, contains as much 
water as is found in the uncropped plots for the same depth. It would 
seem, then, that the cowpea plant is a comparatively deep feeder and the 
shade of its leaves serves as a blanket to prevent evaporation. This con¬ 
clusion is again borne out by a study of the moisture content of the soil 
under the artificial shade. 
Now, since only the moisture in the first foot could possibly affect the 
degree of compactness or of looseness at any one time, a direct comparison 
